Stereoselective synthesis of vinylic chalcogenides through vinylic substitution by lithium organylchalcogenolates

Enol phosphates and enol tosilates of β-dicarbonyl compounds react with lithium organoselenolates to give β-organoseleno (Z)-α,β-unsaturated carbonyl compounds. Tetrasubstituted vinylic vic-bis(organylchalcogenides) of (E)-geometry have been prepared by this method.     

A simple and effective approach to the synthesis of alkynyl selenides from terminal alkynes

Alkynyl selenides were prepared under very mild conditions by reacting terminal alkynes with respective diorganic diselenides in the presence of potassium t-butoxide.The advantages of this protocol include the use of readily available substrates and reagent and good yield of the products.     

Hydroselenation of alkynes using NaBH4/BMIMBF4: easy access to vinyl selenides

A general and easy method for the synthesis of several vinyl selenides using NaBH₄ and BMIMBF₄ as a recyclable solvent is described. This efficient and improved method furnishes the corresponding vinyl chalcogenides preferentially with Z configuration. We also observed that when the same protocol was applied to phenyl acetylene, (E)-bis-phenylseleno styrene was obtained in good yield and with high selectivity.     

A simple and general preparation of vinylic sulfides, selenides and tellurides

A general method for the synthesis of vinylic chalcogenides by nucleophilic and Ni-catalyzed vinylic substitution on vinylic halides by phenyl chalcogenolates is described. The reactions were regio and stereoselective for the nickel catalyzed substitution, and mixture of isomers was observed for some examples in the thermal process in DMF.     

Transition-metal free synthesis of diaryl vinyl selenides: a simple synthetic approach with high selectivity

A simple, highly efficient synthetic protocol is developed for the synthesis of unsymmetrical diaryl vinyl selenides from diaryldiselenide and β-bromo styrene under transition-metal free conditions in N,N′-dimethyl propylene urea and 130 °C to afford high yields and excellent selectivities. This method provides a new strategy to fabricate a wide variety of important substituted molecular skeletons and an alternative to conventionally used metal salts, additives, and ligands.     

铟促进的烯丙基硒醚的合成

烯丙基溴和炔丙基溴在铟促进下与二硒化合物反应，生成烯丙基和炔丙基硒醚。反应无需严格的无水无氧条件，烯丙基溴以α-位与二硒化合物反应，产率55%～91%。     

A facile stereoselective synthesis of (E)‐1,2‐disubstituted vinylic selenides via hydromagnesiation of alkylarylacetylenes

Hydromagnesiation of alkylarylacetylenes 1 in diethyl ether gave (E)‐α‐arylvinyl Grignard reagents 2 , which reacted with arylselenenyl bromides 3 in THF to afford stereoselectively (E)‐1,2‐disubstituted vinylic selenides 4 in good yields. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:65–68, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20066     

Indium(I) iodide promoted cleavage of diphenyl diselenide and disulfide and subsequent palladium(0)-catalyzed condensation with vinylic bromides. A simple one-pot synthesis of vinylic selenides and sulfides

[reaction: see text] Diphenyl diselenide (and disulfide) undergo facile reaction with indium(I) iodide and the corresponding intermediate complex condenses in situ with a variety of substituted vinyl bromides in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium(0) [Pd(PPh3)4] in THF at room temperature to produce vinylic selenides and sulfides in good yields. The conversion of (E)-vinyl bromides is remarkably stereoselective giving (E)-vinyl selenides (and sulpfides) whereas the stereoselectivity in reaction of (Z)-vinyl bromides is not very good.     

Flow chemistry approach for partial deuteration of alkynes: synthesis of deuterated taxol side chain

The partial deuteration of alkynes proceeds via a flow chemistry approach under Lindlar’s heterogeneous catalysis to provide cis-dideuterated olefins in good yields. Further, dideuterated olefin has been successfully utilized for Sharpless asymmetric dihydroxylation followed by Mitsunobu reaction for the synthesis of deuterated taxol side chain.     

Radical cyclization of vinylic ethers: expedient synthesis of (+)-monocerin

Stereoselective synthesis of (+)-monocerin was accomplished via radical cyclization of a vinylic ether intermediate.     

Hydrothiolation of terminal alkynes with diaryl disulfides and diphenyl diselenide: selective synthesis of (Z)-1-alkenyl sulfides and selenides

A simple, stereoselective and efficient method for the hydrothiolation of terminal alkynes with diaryl disulfides and diphenyl diselenide has been developed. In the presence of CuI, rongalite, and Cs₂CO₃, a variety of disulfides underwent the reaction of terminal alkynes stereoselectively to afford the corresponding (Z)-1-alkenyl sulfides in moderate to excellent yields. It is noteworthy that hydroselenations of 1,2-diphenyldiselane with alkynes are also conducted smoothly to afford (Z)-1-alkenyl selenides in good yields under the standard conditions.     

Facile synthesis of fluorinated α-imino alkynes by the coupling reaction of imidoyl iodides with terminal alkynes

A series of N-arylbromodifluoroacetimidoyl iodides and 1-alkynes were converted into α-imino alkynes by using Pd(Ph₃)₂Cl₂/CuI as the catalyst under mild conditions. The reaction proceeded smoothly to give the coupling products in good to excellent yields.     

Heck-type 5-endo-trig cyclization promoted by vinylic fluorines: synthesis of 5-fluoro-3H-pyrroles

A 5-endo-trig alkene insertion proceeds under palladium catalysis via aminopalladium species starting from 3,3-difluoroallyl ketone O-pentafluorobenzoyloximes, providing a facile access to 5-fluoro-3H-pyrroles.     

Short and efficient preparation of alkynyl selenides, sulfides and tellurides from terminal alkynes

Diphenyl diselenide reacts with terminal alkynes at room temperature in DMSO in the presence of catalytic amounts of copper iodide to give good to excellent yields of alkynyl phenyl selenides. The reaction occurs under neutral conditions and the solvent acts as the oxidant. Diphenyl disulfide and ditelluride undergo the analogous reaction, but require the presence of a weak inorganic base.     

Application of organic selenides and tellurides in organic synthesis

This paper describes the progress on the synthesis of organic selenides and tellurides and their application in organic synthesis.Low valent selenium and telluronium compounds having high reducing selectivity can be used to form carbon-hydrogen bonds as special reducing reagents.Telluronium ylides can react with aldehydes and ketones by Wittig-type condensation to produce (E)-configuration alkenes stereoselectively.α-Phenylselanyl arsonium ylides were prepared by transyl-idation reaction of arsonium ylides with phenylselanyl halides which can undergo Wittig-type reactions with carbonyl compounds to give (Z)-α-selanyl-α,β-unsaturated compounds with high stereoselectiv-ity.Zirconium,tin,boron,halogen,metal or hetero-atom were introduced in organoselenium and telluronium compounds as new difunctional group reagents.Under transition metal catalysis,the corresponding cross coupling reactions provide new methods of formation of carbon-carbon double bonds,which were used in the stereoselective synthesis of     

Pd-promoted vinylic hydrogen substitution of alkene and α carbonylated alkene by lithium and magnesium organocuprates.

In the presence of PdCl₂, LiCl and K₂CO₃, vinylic hydrogen substitution of styrene and acrylic ester, in MeCN and MeCN - HMPA respectively, has been successfully performed using lithium and magnesium organocuprates.     

One-pot synthesis of dihydropyrimidinones catalysed by lithium bromide: an improved procedure for the Biginelli reaction

LiBr catalyses efficiently the three component condensation reaction of an aldehyde, a β-ketoester and urea in refluxing acetonitrile to afford the corresponding dihydropyrimidinones in high yield.     

Synthesis of highly substituted 1,3-dienes and 1,3,5-trienes by the palladium-catalyzed coupling of vinylic halides,internal alkynes,and organoboranes

[reaction: see text] Highly substituted 1,3-dienes and trienes have been prepared in good to excellent yields by the palladium-catalyzed coupling of vinylic halides, internal alkynes, and organoboranes.